摘要
精神发育迟滞(Mental retardation, MR)是人类精神系统疾病的一种,具有一定的遗传基础。地处陕、川、甘、鄂、豫的秦巴山区是我国主要的贫困地区之一,也是我国精神发育迟滞疾病的高发地区之一,深入研究当地精神发育迟滞的遗传病因,是一件具有实际意义和理论意义的工作。本论文从基因组水平出发,以秦巴山区汉族MR家系人群为研究样本,采用SYNGAP1基因和UPF3B基因作为候选基因进行关联分析,以研究这两个基因与秦巴山区MR的关系。
SYNGAP1基因编码蛋白为大脑中特异性表达的GTP活性蛋白,通过抑制Ras蛋白活性,对其下游信号传导通路进行调控,同时作为NMDA受体蛋白复合体的重要组成部分,参与神经突触可塑性。(?)JPF3B基因编码蛋白作为剪接后蛋白复合体的一部分,参与mRNA的出核运输和无义密码子介导的mRNA降解(nonsense mediated mRNA decay, NMD)过程。鉴于以上两个基因在人体中的重要功能,我们怀疑它们的有害突变可能与中国秦巴山区汉族人群MR有所关联。本研究设计了一个来自中国秦巴山区MR核心家系人群的,由456份DNA样品组成的研究样本；并选取了SYNGAP1基因上的8个SNP位点和UPF3B基因上的5个SNP位点作为遗传标记,在核心家系样本中进行了关联分析。
本研究采用PCR-RFLP和PCR-SSCP并结合测序的方法对标记位点进行基因分型,获得分型数据后采用Microsoft Excel 2007软件对家系数据进行录入和统计,使用Haploview 4.1软件进行HWE检验、连锁不平衡分析(LD)及传递不平衡检验(TDT),使用UNPHASE3.13软件进行HRR和HHRR分析,最后使用G*power 2.0软件计算统计效力。
在对SYNGAP1基因的研究中：分析结果显示8个标记位点均符合HWE平衡；依据LD分析结果划分了两个单倍型块：跨度2kb的由SNP位点rs75045763-rs453590组成的单倍型块1和跨度13kb的由SNP位点rs411136-rs12204193-rs2247385组成的单倍型块2,其余3个SNP位点：rs2076775、rs9394145和rs10807124由于同其他标记位点的连锁程度较低并没有位于划分的单倍型块中；TDT分析结果显示标记位点rs10807124存在显著传递不平衡现象(P=0.0071)；HRR分析和HHRR分析中,也显示出该位点的多态性与MR存在阳性相关(PHRR=0.0067,PHHRR=0.0148);其他7个标记位点TDT、HRR、HHRR关联分析结果均显示它们的多态性与MR无关(P>0.05)；单倍型分析结果显示,两个单倍型块的多态性也与MR无显著相关。在对UPF3B基因的研究中,分析结果显示5个标记位点均符合HWE平衡；依据LD分析结果划分了一个由SNP位点rs2496207-rs2285552组成的单倍型块,其余3个SNP位点：rs2239963、rs5910682和rs5910686由于同其他标记位点的连锁程度较低并没有位于划分的单倍型块中；TDT分析、HRR分析、HHRR分析以及单倍型分析结果均显示该基因各标记位点和单倍型的多态性与MR无显著相关(P>0.05)。
本次研究的结论为：SYNGAP1基因的标记位点rs10807124与秦巴山区汉族人群MR相关,提示在该标记位点附近的连锁区域内很可能存在着影响基因功能的突变位点,而这种有害突变很可能是造成秦巴山区人群患有MR病症的遗传原因之一；UPF3B基因的标记位点与秦巴山区汉族人群患有MR病症无关,也可以说该基因不是秦巴山区MR的主要致病基因。当然,本次研所得的结论只是初步结论,需要在日后进行更深一步的研究加以验证。
Mental retardation (retardation, MR), effected by certain genetic factors, is a human mental disorder. Qinba mountain region located at the interspace of Shaanxi, Sichuan, Gansu and Hubei province, is one of the main impoverished regions of China and is also a high-risk area for the mental retardation disease. So, revealing the genectic causes of local mental retardation disease is significant from practical and theoretical points of role. In present study, the SYNGAP1 gene and UPF3B gene were selected as candidate genes, and the 13 SNPS sites were selected as genetic markers, to study the relationship between polymorphism of the above genes and MR risk in the Chinese Han population of Qinba mountain region.
SYNGAP1 gene encoding protein is a special GTP active protein expressed in brain. It acts by inhibiting the activity of Ras protein, which therefore controls its downstream signaling pathways. SYNGAP1 gene encoding protein also participates in the process of neural synaptic plasticity as an important member of protein complex for the NMDA receptors. UPF3B genetic encoding protein participates in outer nuclear transport process of mRNA and nonsense codon mediated mRNA degradation (NMD) process. In view of the important function of the SYNGAP1 gene and UPF3B gene to human, it is hypothesized that the polymorphism of the two genes may correlate with MR susceptibility of Chinese Han population of Qinba mountain region. A study based on the nuclear pedigree for 456 samples from Chinese Han population of Qinba mountain region was performed, using thirteen SNPs sites in the two genes, with the aim to investigate the relationship between their polymorphism and MR susceptibility.
The PCR-SSCP, PCR-RFLP and sequencing methods were used in the genotyping of the markers. Later, the nuclear pedigree datas were treated with Microsoft Excel 2007. The Hardy-Weinberg equilibrium (HWE), linkage disequilibrium (LD) block structure and TDT analysis were performed by Haploview 4.1. The HRR and HHRR analysis were performed by UNPHASE 3.13, and statistical power analysis was performed using the G*Power 2.0 program.
In the study of SYNGAP1 genes, the results show that the eight markers are all in HWE balance; Linkage disequilibrium (LD) analysis revealed that the rs75045763-rs453590 and rs411136-rs12204193-rs2247385 were in strong LD, separately; The TDT analysis show that the marker rs10807124 was over-transmission from parents to MR offspring (P= 0.0071);HRR analysis and HHRR analysis of rs10807124 also shows positive results (PHRR=0.0067, PHHRR=0.0148); The other seven markers on SYNGAP1 gene are shows negativeresults in HHRR, TDT and HRR analysis (P>0.05);haplotype analysis shows that the polymorphism of the two blocks are not association with the MR in Qinba mountains.In the study of UPF3B genes, the results show that the five markers are all in HWE balance; Linkage disequilibrium (LD) analysis revealed that the rs2496207-rs2285552 were in strong LD; The result shows that all five markers polymorphism are not association with the MR in Qinba mountains in TDT analysis, HRR analysis, HHRR analysis and haplotype analysis (P>0.05).
The resultes indicate SYNGAP1 gene polymorphism closely correlated with MR risk in Chinese Han population of Qinba mountain region, it was supposed that mutation on this gene lead to MR disease in Qinba mountain region; UPF3B gene polymorphism showed negative correlation with MR desease in Chinese Han population of Qinba mountain region, and mutation on this gene is not a major genetic reason for MR desease. And detail studies are still needed in future.
引文
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